Science Filmmaking to Test Ape Memory

A career in science has never been easy to pursue. There are all those years of graduate school, postdoctoral research positions that don’t necessarily lead to a faculty appointment, long hours and competition for grant money.

Two Japanese researchers have taken dedication to new heights, however. For the purposes of testing ape memory, they wrote, directed and starred in two short videos made for viewing by chimpanzees and bonobos. They report in a recent paper in Current Biology that apes can indeed remember an event after seeing it only once.

This is not a great surprise, but it plays into a continuing debate about what, exactly, nonhuman animals can remember.

In one of the laboratory of the apes movies, the two researchers, Fumihiro Kano and Satoshi Hirata of Kyoto University, wave at each other and the camera, and then each moves in an apelike fashion to positions near small doors, one on the left and one on the right. An actor in an ape suit comes through the door on the right and pounds on the back of Dr. Kano with his fists. Then he retreats through the door, and Dr. Kano follows. The other video has a slightly different plot that also involves an “ape suit guy,” as Dr. Kano described him, and aggression.

The researchers showed the videos to bonobos and chimpanzees, waited 24 hours and showed them the same videos again. They used eye-tracking software to record what the apes were watching. In the second viewing, the apes clearly concentrated from the start on the right door, not the left, showing that they remembered and anticipated the attack. In effect, their eye movements translated to, “Here comes the good part!”

In the other video, on the second viewing they concentrated on a hammer, which was destined to play a part in an act of retaliation against the “ape suit guy.”

Dr. Kano said the researchers created story lines with aggression because apes, like humans, are more likely to fix in memory events that have strong emotions attached. And apes are excited by aggression. The researchers also knew from previous work that apes don’t like the “ape-suit guy.”

The reason for the study, Dr. Kano said, was a debate in science about memory in nonhuman animals. Some scientists question “whether nonhuman animals freely recall single events,” he added.

He said the video experiment didn’t answer this question fully. It shows that apes recall events they have seen only once, but the recall is prompted by the video. Still, he said, the findings add to previous research and show that this method works as a way of probing what apes are thinking. He said it could be used to probe other kinds of ape thought processes.

Neither Dr. Kano nor Dr. Hirata are likely to be nominated for acting awards by any human groups. The aggression is stylized and looks comical. “To humans, these videos are just funny,” Dr. Kano acknowledged in an email. But he said the apes took them seriously. “Some apes made a threat voice,” he said, and banged on a panel in front of them.

But, he wrote, like humans, they knew the difference between a movie and reality. “I’ve never seen that they were seriously scared with the video content.”